The current world-wide energy shortage has stimulated a need for more energy efficient domestic appliances of all kinds. This need is particularly critical in connection with heating systems for domestic hot water because such systems are among the heaviest consumers of energy on a year round basis.
The present invention seeks to satisfy the need for an energy conserving domestic water heating system by recovering and utilizing heat which heretofore has been wasted into the atmosphere through the furnace flue and/or the warm air outlet of the air conditioning condenser unit. In a variant of the invention, heat is recovered from the return line for hot refrigerant in an air conditioning unit and is utilized through a heat exchange means in the domestic water heating system.
The system embodying the invention also employs a circulating pump which is controlled through a relay to a standard thermostat, whereby when the thermostat is calling for either heating or cooling the pump will be energized, and at other times the pump will be de-energized. By means of the invention, water which is preheated by utilization of normally wasted heat energy can be stored in the separate storage tank at a temperature in the range of 145.degree.-165.degree. F. and this preheated water will be injected into the inlet of the domestic water heater so that the latter may have its thermostat lowered from the usual 130.degree.-140.degree. F. to approximately 100.degree.-110.degree. F. The hot water heater is only required to work when the furnace or air conditioning unit is not running enough to supply all needed hot water, thus resulting in a very substantial savings on energy costs to the consumer.
The invention can be installed in either new or existing hot water heating systems on an economical basis and amortization is estimated to be three to five years on average.
The prior art contains a number of teachings relative to the recovery of waste heat energy and/or the use of heat exchanger means in conjunction with domestic water heaters. Generally, the prior art devices have been excessively costly to install and have not been compatible with existing equipment as is the case with the present invention. Furthermore, the known prior art devices do not possess the full capabilities of the invention in one simplified system for selectively utilizing wasted energy in the furnace flue or in air conditioning equipment through employment of a separate water storage tank, associated system valving, and a circulating pump as will be fully described in the following detailed description.